July 15, 1942
ANALYTICAL EDITION
typical. They certainly corroborate Reiner’s prediction of linearity, and also prove the existence of definite thixotropic levels. The fact that the down curves are linear above Ti means that U and f are constant above this point and can readily be determined from the simple linear equations, 4 and 5. These facts, in the opinion of the writer, justify the use of a properly constructed rotational viscometer and the application of the Reiner equation for industrial rheological measurements and calculations.
Acknowledgment The author is indebted to Interchemical Corporation for permission to publish this work, t o Ruth N. Weltmann who supervised the production of the laboratory data and gave valuable advice on the construction of the viscometer, and t o Daniel Smith.
585
Literature Cited (1) Bingham, E. C., Bur. Standards, Sci. Paper 278 (1916). (2) Bingham, E. C., and Green, Henry, Proc. Am. SOC.Testing Materials, 19,Part 11, 640-75 (1919). (3) Buckinsham. E.. Ibid.. 21. 1154 (1921). (4) Goodeve, C. ‘F.,’andWhitfield, G. W’., Trans. Faraday Soc., 34, 511-20 (1938). ( 5 ) Green, Henry, IND. ESG. CHEX.,A N . ~ LED., . 13,632 (1941). (6) Green, Henry, Paper Trade J., 114,No.6, 39 (Feb. 5, 1942). (7) Green, Henry, Proc. Am. SOC.Testing Materials, 20, Part 11, 461-94 (1920). (8) Green, Henry, and Haslam, G. S.,IND.ENG.CHEM.,17, 726 (1925). (9) Hatschek, E., Kolloid-Z., 13,88-96 (1913). (10) Mooney, M., and Ewart, R. H., Physics, 5, 360-4 (1934). (11) Ostwald, W., and Stuart, W. W., Kolloid-Z., 78,324 (1936). (12) Reiner, Markus, J . Rheology, 1, 5-9 (1929). (13) Reiner, Markus, Physics, 5 , 3 2 1 4 1 (1934).
Simplified Apparatus for Catalase Determination ROBERT R. THO3IPSON New York State Agricultural Experiment Station, Gene\a, S . 1..
A
M E T H O D of simply and rapidly determining t h e extent of inactivation of the enzyme catalase, after the blanching process and before dehydration or freezing of vegetables, is presented. Xorgarrd ( d ) , Knott ( I ) , Pack (S), and Tressler and Evers (4) have described methods for catalase assay based on the amount of oxygen liberated b y the action of the enzyme on hydrogen peroxide. While these methods are accurate, Nor-
garrd’s requires too long a time to complete the reaction, Knott and Pack’s both require specialized apparatus, while the method devised by Tressler and Evers, though satisfactory upon the whole, will not give accurate results with all vegetables. By using a modification of the Tressler procedure, eliminating the fermentation tube and substituting the apparatus illustrated in Figure 1, the extent of inactivation can be determined accurately in 2 minutes, and the apparatus is simple to construct and inexpensive. Such a method should have value, especially in food-processing plants where it is necessary to make catalase determinations in a minimum period of time. The Canadian Government requires catalase tests run on all vegetables after blanching as a quality control measure for the dehydrated products. PROCEDURE. An accurately weighed 1.0 gram sample is ground in a mortar with 0.6 gram of calcium carbonate and 1.0 gram of fine sand. Ten milliliters of water are added and the grinding is continued for about 2 minutes. One milliliter of this mixture is pipetted into one half of the special divided flask, and 2 ml. of hydrogen peroxide (Diosygen) are placed in the other half. The flask is then attached to the manometer and the whole apparatus is suspended in a thermostatically controlled water bath at 20” C. When the apparatus reaches the bath temperature, the stopcock is closed (water level in U-tube set a t 0 ml.) and the apparatus is shaken for 2 minutes. A reading of the pipet is then made to determine the amount of oxygen liberated. The catalase may be reported as milliliters of oxygen liberated by 0.1 gram in 2 minutes. For general use the calculations put forth by Tressler and Evers have been found adequate.
This method gives only relative values but is very useful for the estimation of a series of comparisons. It mas designed for rapid factory laboratory use, but can be used where more quantitative values are desired.
Literature Cited YME
FIGURE1. CATALASE APPARATUS 1. 5-cc. pipet graduated in 0.1 cc., fused to 0-piece of tubing of same diameter 2 . Water in tube, a t 0 cc. level of pipet a t start of reaction 3. Stopcock to adjust level of water after flask is attached 4 . 60-cc. Erlenmeyer flask with divided bottom
(1) Knott, J. E., N. Y . (Ithaca) Agr. Expt. Sta., M e m o 106 (1927). (2) Norgarrd, A. V. S., J . Biol. Chem., 38,501 (1919). (3) Pack, D. A., IND.ENG.CHEM., A N ~ LED., . 4,393 (1932). (4) Tressler, D. K., and Evers, C. F., “Freezing Preservation of Fruits, Fruit Juices, and Vegetables”, p. 228, New York, Avi Publishing Co., 1936. APPROVED by the Director of the New York State Agricultural Experiment Station for publiration as Journal Paper No. 490.
